Underlayments that are installed over sub-floor structures can facilitate the laying of floor coverings, for example, carpet, tile, wood parquet, and vinyl, and may result in a more stable finished floor. Many pourable floor topping mixtures, which are suitable for incorporation in underlayment systems, are gypsum-based, in order to provide a level of fire protection by retarding the spread of flames. Some examples of gypsum-based floor topping mixtures include: Gyp-Crete®, Gyp-Crete 2000® and Dura-Cap®, all of which are available from Maxxon® Corporation. Gypsum-based pourable floor topping are generally installed in dwellings, which are under construction and subject to building codes that require minimum fire ratings.
Pourable floor toppings are typically installed in two stages: first, over the portions of a dwelling sub-floor where fixtures such as bath tubs are to be installed (these portions being designated as pre-pour areas); and, then, over the remainder of the sub-floor, following the installation of the fixtures. Although the pre-pour areas are relatively small compared to the remainder of the sub-floor, installation of the pourable floor topping to the pre-pour areas requires dispatching to the construction site all of the necessary equipment and crew that, subsequently, must be dispatched again, after installing the bath tubs, in order to install the remainder of the floor topping to complete the underlayment system.